1. Field of the Invention
The present invention relates to a camera system, a camera body, and a communication method, and particularly, to a communication technology between the camera body and the interchangeable lens.
2. Description of the Related Art
Recent digital cameras capable of high-quality video capturing of a full-high definition video (Full-HD video) or the like have been widespread with increasing speed of an imaging element. Similarly, a camera with an interchangeable lens is also capable of high-quality video capturing, but in order to perform image processing on a video according to lens characteristics, a camera body needs to acquire lens information (for example, focus position information, diaphragm information, and zoom information) for each frame during video capturing.
Further, there is conventionally a communication method in which a camera body sends a request to a lens unit (interchangeable lens) periodically regardless of a frame rate of a video so as to confirm whether or not there is a change in a lens state, and the interchangeable lens sends a response regarding the lens state of an item in which there is a change, to the camera body. Accordingly, the lens information in video capturing is acquired and reflected in signal processing or the like.
However, driving of the lens may be normally required during video recording, and it is difficult to acquire the lens information always at regular intervals.
Meanwhile, in an invention described in JP2012-58524A, two systems of transfer paths (first transfer path and second transfer path) are provided between a camera body and an interchangeable lens, so that hotline communication is performed using the first transfer path, and command data communication is performed using the second transfer path.
Here, the hot line communication is unidirectional communication for transferring lens information from the interchangeable lens to the camera body in each period (for example, 1 ms) using the first transfer path, and the command data communication is bidirectional communication for transferring data transmitted from the camera body and data transmitted from the interchangeable lens using the second transfer path.
Meanwhile, in a camera system including a camera body and an interchangeable lens, a technology in which a camera body requests the interchangeable lens to provide optical transfer function (OTF) data that is a two-dimensional Fourier transform of a point spread function (PSF), which is used for a point image restoration process of a captured image from the camera body, and the interchangeable lens acquires lens setting information such as a zoom position, a diaphragm value (F value), and a subject distance in response to this request, reads the OTF data corresponding to the lens setting information from the OTF data stored in the interchangeable lens, and transmits the read OTF data to the camera body is described in JP2012-505562A.
Further, in WO2009/139118A, a camera system in which a camera body switches between a synchronous mode in which a synchronization signal generated by the camera body is transmitted to an interchangeable lens and an operation of the interchangeable lens is controlled in synchronization with the synchronization signal and an asynchronous mode in which the operation of the interchangeable lens is controlled without synchronization with the synchronous signal generated by the camera body is described.
The camera body described in WO2009/139118A performs switching to the synchronous mode when a video (including a live-view image) is captured, and performs transmission and reception of lens information necessary for auto-focus (AF: Automatic Focus) control or automatic exposure (AE) control in synchronization with the synchronization signal. On the other hand, the camera body performs switching to the asynchronous mode when still image capturing is executed, such that image processing or the like can be focused upon.